The present invention relates to implantable medical devices and more particularly to methods of their manufacture.
The earliest pacemakers, for example as disclosed in U.S. Pat. No. 3,057,356 to Greatbatch, were manufactured of discrete electronic components which were potted in an epoxy resin material and then coated with silicone rubber. Continued progress in the development of heart pacemakers resulted in packaging concepts in which the electronic circuitry portion of the pacemaker was enclosed in a sealed metal container which was coupled to batteries outside the container. The batteries and sealed container were potted in epoxy to form the pacemaker.
Development of the solid state lithium iodide battery permitted the inclusion of the electrochemical cell within a hermetic metal housing. Such a pacemaker is disclosed in U.S. Pat. No. 4,314,562. In most such pacemakers, the pacemaker housing is formed from two metal halves, which form a "clam shell" assembly. The housing halves are typically butt welded together along their edges. Electrical communication to pacing and sensing electrodes in such pacemakers is accomplished using a rigid plastic connector module fixed to the outer surface of the housing and one or more feedthroughs which permit electrical communication to and from circuitry within the housing while retaining hermeticity of the pacer. This pacemaker architecture has become conventional, and has resulted in reliable long lived pacemakers. This basic architecture has also been employed to produce other types of implantable devices such as implantable defibrillators, nerve stimulators, drug pumps and physiologic monitors.
Construction of pacemakers or other implantable medical devices using the basic architecture described above has required solution of a variety of problems, the solutions to which in turn often require complex manufacturing operations which increase costs, lower yields and limit design freedom. Such manufacturing operations may include: the use of weld rings to protect internal components during butt welding operations to join the housing halves; welding interconnections between the battery, circuitry and feedthroughs; location of feedthroughs in areas adjacent to or on the seam joining the housing halves; fabrication of cups or spacers to locate the battery and circuitry within the housing; molding of plastic connector modules around electrical connector blocks and cosmetic buffing operations to improve the appearance and biocompatibility of the enclosure.